Zero-Crossing Detection (ZCD) is a subsystem in some synchronous Integrated DC/DC Power Converters, particularly DC/DC Stepdown Converters (Buck). Forced CCM (Continuous Conduction Mode) operation is often undesired compared to DCM (Discontinuous Conduction Mode), due to huge efficiency drops, usually in the mid-load/low-load range.
Overload Detection (OVL) plays a role in synchronous Integrated DC/DC Power Converters as well. OVL provides a limiting current mechanism across the low-side power switch of a buck converter, and prevents current runaways in case of buck converters having an output shorted to ground.
Many conventional synchronous converters do not use zero-crossing detection, and instead use forced CCM, because the complexity of zero-crossing detection can potentially introduce risks, accuracy issues, and critical control.